Semantic Parsing of Objects in Video

ABSTRACT

Methods, systems, and computer program products for parsing objects in a video are provided herein. A method includes producing a plurality of versions of an image of an object, wherein each version has a different resolution of said image of said object, and computing an appearance score at each of a plurality of regions on the lowest resolution version for at least one semantic attribute for said object. Such a method also includes analyzing one or more other versions to compute a resolution context score for each of the plurality of regions in the lowest resolution version, wherein said resolution context score denotes an extent to which finer spatial structure exists in the one or more others versions than in the lowest resolution version, and determining a configuration of the at least one semantic attribute in the lowest resolution version based on the appearance score and the resolution context score.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/783,749, filed Mar. 4, 2013, which is a continuation of U.S. patentapplication Ser. No. 12/845,095, filed Jul. 28, 2010, both of which areincorporated by reference herein.

The present application is related to U.S. patent application entitled“Multispectral Detection of Personal Attributes for Video Surveillance,”identified by Ser. No. 12/845,121 and filed Jul. 28, 2010, thedisclosure of which is incorporated by reference herein in its entirety.

Additionally, the present application is related to U.S. patentapplication entitled “Facilitating People Search in Video Surveillance,”identified by Ser. No. 12/845,116, and filed Jul. 28, 2010, thedisclosure of which is incorporated by reference herein in its entirety.

Also, the present application is related to U.S. patent applicationentitled “Attribute-Based Person Tracking Across Multiple Cameras,”identified by Ser. No. 12/845,119, and filed Jul. 28, 2010, thedisclosure of which is incorporated by reference herein in

FIELD OF THE INVENTION

The invention relates to video processing and object identification, andmore particularly relates to analyzing images of objects to identifyattributes.

BACKGROUND

Automatically identifying the locations of objects and their parts invideo is important for many tasks. For example, in the case of humanbody parts, automatically identifying the locations of human body partsis important for tasks such as automated action recognition, human poseestimation, etc. Body parsing is a term used to describe thecomputerized localization of individual body parts in video. Currentmethods for body parsing in video estimate only part locations such ashead, legs, arms, etc. See e.g., “Strike a Pose: Tracking People byFinding Stylized Poses,” Ramanan et al., Computer Vision and PatternRecognition (CVPR), San Diego, Calif., June 2005; and “PictorialStructures for Object Recognition,” Felzenszwalb et al., InternationalJournal of Computer Vision (IJCV), January 2005.

Most previous methods in fact only perform syntactic object parsing,i.e., they only estimate the localization of object parts (e.g., arms,legs, face, etc.) without efficiently estimating semantic attributesassociated with the object parts.

In view of the foregoing, there is a need for a method and system foreffectively identifying semantic attributes of objects from images.

SUMMARY

The invention resides in a method, computer program product, computersystem and process for estimating parts and attributes of an object invideo. The method, computer program product, computer system and processcomprising producing a plurality of versions of an image of an objectderived from a video input, wherein each version has a differentresolution of said image of said object, and computing an appearancescore at each of a plurality of regions on the lowest resolution versionof said plurality of versions of said image for at least one semanticattribute for said object, wherein said appearance score denotes aprobability of the at least one semantic attribute appearing in theregion. Such techniques also include analyzing one or more otherversions of the multiple versions to compute a resolution context scorefor each of the plurality of regions in the lowest resolution version,wherein said resolution context score denotes an extent to which finerspatial structure exists in the one or more others versions than in thelowest resolution version for each of the plurality of regions, anddetermining a configuration of the at least one semantic attribute inthe lowest resolution version based on the appearance score and theresolution context score in each of the plurality of regions in thelowest resolution version.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

These and other features of the invention will be more readilyunderstood from the following detailed description of the variousaspects of the invention taken in conjunction with the accompanyingdrawings that depict various embodiments of the invention, in which:

FIG. 1 shows an illustrative environment for a system for detectingsemantic attributes of a human body according to an embodiment of theinvention.

FIG. 2 shows a close up of an illustrative environment for detectingsemantic attributes in human body in video according to an embodiment ofthe invention.

FIG. 3 illustrates an example of input and output according to anembodiment of the invention.

FIG. 4 shows an illustrative data flow for detecting semantic attributeson an image according to an embodiment of the invention.

FIG. 5 shows examples of semantic attributes being associated with bodyparts according to an embodiment of the invention.

FIGS. 5A and 5B show examples of applying semantic attributes to a humanbody image according to an embodiment of the invention.

FIG. 5C shows examples of evaluating appearance scores according to anembodiment of the invention.

FIG. 5D shows inputs and outputs for the step of computing appearancescores according to an embodiment of the invention.

FIGS. 6 and 6A show examples of computing resolution context scoresaccording to an embodiment of the invention.

FIG. 6B shows inputs and outputs for the step of computing resolutioncontext scores according to an embodiment of the invention.

FIGS. 7A and 7B show examples for computing geometric scores for anoptimal configuration according to an embodiment of the invention.

FIG. 7C shows inputs and outputs for the step of computing geometricscores according to an embodiment of the invention.

FIG. 8 shows inputs and outputs for the step of computing a total scoreaccording to an embodiment of the invention.

It is noted that the drawings are not to scale. The drawings areintended to depict only typical aspects of the invention, and thereforeshould not be considered as limiting the scope of the invention. Whilethe drawings illustrate the processing of human bodies in video, theinvention extends to the processing of other objects in video. In thedrawings, like numbering represents like elements between the drawings.

DETAILED DESCRIPTION

The invention relates to video processing and object identification, andmore particularly relates to analyzing images of objects to identifyattributes.

Aspects of the invention provide an improved solution for detectingsemantic attributes of objects in video. For example, aspects of theinvention provide for the extraction of attributes from body parts toenable automatic searching of people in videos based on a personaldescription. In another example, the invention provides for theextraction of attributes from cars to enable automatic searching of carsin video based on a description of a car. A possible query could be:“show all people entering IBM last month with beard, wearing sunglasses,wearing a red jacket and blue pants” or “show all blue two-door Toyotawith diamond hub caps entering the IBM parking lot last week.”

The invention deals with the problem of semantic object parsing, wherethe goal is to effectively estimate both part locations and semanticattributes in the same process. Using human body parsing as an example,embodiments of the invention provide for the estimation of semanticattributes of human body parts together with the localization of bodyparts in the same process. Overcoming the inefficiency and inaccuracy ofthe previous approaches, the invention leverages a global optimizationscheme to estimate both parts and their corresponding attributessimultaneously.

Unlike previous approaches, embodiments of the invention use semanticattributes such as “beard,” “moustache,” and “no facial hair” to notonly locate the human body part but also identify the attribute of thebody part. For example, instead of only identifying a body part such asa “leg,” the invention uses semantic attributes such as “blacktrousers,” “long skirts,” and “shorts” to both locate the body part andidentify its attributes. The invention maintains a data table relatingeach semantic attribute to a corresponding body part. For example, thesemantic attribute “beard” corresponds to the body part “lower faceregion.”

Embodiments of the invention are based on three kinds of features:appearance features, resolution context features, and geometricfeatures. The appearance features refer to the scores obtained bycomparing semantic attributes from an image library to what appears tobe on the image to evaluate the probability of a match. The resolutioncontext features refer to object consistency under different imageresolutions. The resolution context score for a particular region is theweighted average score from the particular region's higher resolutionimage. A total score is computed for the higher resolution image byadding up the appearance scores, geometric scores and if, a higherresolution image is available, resolution context scores. The resolutioncontext score is computed from a higher resolution image as the totalscore at a given region divided by the number of sub-regions whichcompose that region on the higher resolution image being analyzed. Thegeometric features refer to the scores computed based on the spatialrelationships among the underlying parts in a probable configuration.For example, a potential attribute of “beard” corresponds to a “face”and a “black shirt” corresponds to a “torso.” The geometric featurestest the accuracy of the candidate semantic attributes by applying thegeneral human body configuration principle that a “face” is both above a“torso” and of a certain distance from a “torso.”

In the example of human body parsing, aspects of the invention estimatenot only human body part locations, but also their semantic attributessuch as color, facial hair type, presence of glasses, etc. In otherwords, aspects of the invention utilize a unified learning scheme toperform both syntactic parsing, i.e., location estimation, and semanticparsing, i.e., extraction of semantic attributes that describe each bodypart. The invention detects both body parts and attributes in the sameprocess to more accurately identify the attributes of a human body overthe prior art.

Turning to the drawings, FIG. 1 shows an illustrative environment fordetecting semantic attributes of a human body according to an embodimentof the invention. To this extent, at least one camera 42 captures ascene, or background 90. Often, the background, or scene 90 may includeat least one object, such as person 92. A digital video input 40 isobtained and sent to a system 12that includes, for example, a semanticattribute detection program 30, data 50, predetermined or specifiedsemantic attributes 52, output 54 and/or the like, as discussed herein.

FIG. 2 shows a closer view of an illustrative environment 10 fordetecting semantic attributes of person 92 (FIG. 1) in video 40according to an embodiment of the invention. To this extent, environment10 includes a computer system 12 that can perform the process describedherein in order to detect semantic attributes of person 92 in video 40.In particular, computer system 12 is shown including a computing device14 that comprises a semantic attribute detection program 30, which makescomputing device 14 operable for detecting semantic attributes of person92 (FIG. 1) in video 40, by performing the process described herein.

Computing device 14 is shown including a processor 20, a memory 22A, aninput/output (I/O) interface 24, and a bus 26. Further, computing device14 is shown in communication with an external I/O device/resource 28 anda non-transitory computer readable storage device 22B (e.g., a harddisk, a floppy disk, a magnetic tape, an optical storage such as acompact disc (CD) or a digital video disc (DVD)). In general, processor20 executes program code, such as semantic attribute detection program30, which is stored in a storage system, such as memory 22A (e.g., adynamic random access memory (DRAM), a read-only memory (ROM), etc.)and/or storage device 22B. While executing program code, processor 20can read and/or write data, such as data 36 to/from memory 22A, storagedevice 22B, and/or I/O interface 24. A computer program productcomprises the storage device 22B on which the program code is stored forsubsequent execution by the processor 20 to perform a method forestimating parts and attributes of an object in video. Bus 26 provides acommunications link between each of the components in computing device14. I/O device 28 can comprise any device that transfers informationbetween a user 16 and computing device 14 and/or digital video input 40and computing device 14. To this extent, I/O device 28 can comprise auser I/O device to enable an individual user 16 to interact withcomputing device 14 and/or a communications device to enable an element,such digital video input 40, to communicate with computing device 14using any type of communications link. I/O device 28 represents at leastone input device (e.g., keyboard, mouse, etc.) and at least one (e.g., aprinter, a plotter, a computer screen, a magnetic tape, a removable harddisk, a floppy disk).

In any event, computing device 14 can comprise any general purposecomputing article of manufacture capable of executing program codeinstalled thereon. However, it is understood that computing device 14and semantic attribute detection program 30 are only representative ofvarious possible equivalent computing devices that may perform theprocess described herein. To this extent, in other embodiments, thefunctionality provided by computing device 14 and semantic attributedetection program 30 can be implemented by a computing article ofmanufacture that includes any combination of general and/or specificpurpose hardware and/or program code. In each embodiment, the programcode and hardware can be created using standard programming andengineering techniques, respectively. Such standard programming andengineering techniques may include an open architecture to allowintegration of processing from different locations. Such an openarchitecture may include cloud computing. Thus the present inventiondiscloses a process for supporting computer infrastructure, integrating,hosting, maintaining, and deploying computer-readable code into thecomputer system 12, wherein the code in combination with the computersystem 12 is capable of performing a method for estimating parts andattributes of an object in video.

Similarly, computer system 12 is only illustrative of various types ofcomputer systems for implementing aspects of the invention. For example,in one embodiment, computer system 12 comprises two or more computingdevices that communicate over any type of communications link, such as anetwork, a shared memory, or the like, to perform the process describedherein. Further, while performing the process described herein, one ormore computing devices in computer system 12 can communicate with one ormore other computing devices external to computer system 12 using anytype of communications link. In either case, the communications link cancomprise any combination of various types of wired and/or wirelesslinks; comprise any combination of one or more types of networks; and/orutilize any combination of various types of transmission techniques andprotocols.

As discussed herein, semantic attribute detection program 30 enablescomputer system 12 to detect semantic attributes of objects, such asperson 92 (FIG. 1) in video 40. To this extent, semantic attributedetection program 30 is shown including an object detection module 32,an appearance score module 34, a geometric score module 36, a resolutioncontext module 37, a configuration optimization module 38, a computetotal score module 39, and a structured learning module 35. Operation ofeach of these modules is discussed further herein. However, it isunderstood that some of the various modules shown in FIG. 2 can beimplemented independently, combined, and/or stored in memory of one ormore separate computing devices that are included in computer system 12.Further, it is understood that some of the modules and/or functionalitymay not be implemented, or additional modules and/or functionality maybe included as part of computer system 12.

Aspects of the invention provide an improved solution for detectingsemantic attributes of objects, such as person 92 (FIG. 1) in video 40.To this extent, FIG. 3 illustrates an example of the input 90 (FIG. 1)and the output 54 (FIG. 1) according to an embodiment of the invention.As described above (FIG. 1), the input 90 is a scene with at least oneobject, in this example, a person. The output 54 includes spatiallocations of body parts and attributes on an image. For example, theinvention identifies region 402 as the upper face region and identifiesan attribute of the person, “baldness,” from the same region. Region 404is the middle face region and an attribute of “sunglasses” isidentified. Region 406 is the lower face region and an attribute of“beard” is identified. Region 408 is identified as an arm and anattribute of “tattoo” is identified. Region 410 is identified as a legand an attribute of “black trousers” is identified. In addition, theoutput 54 includes a total score and/or a weighted average score of theimage's appearance scores, geometric scores, and resolution contextscores if available, as described herein.

Aspects of the invention provide an improved solution for detectingsemantic attributes of objects, such as person 92 (FIG. 1) in video 40.To this extent, FIG. 4 shows an illustrative data flow for detectingsemantic attributes of person 92 (FIG. 1) on an image by using themodules of semantic attribute detection program 30 (FIG. 2), accordingto an embodiment of the invention. For example, the system 12, at D1,receives digital color video input 40. Digital color video input 40 istypically in red-green-blue (RGB) format and at each time instance aframe of video input with a person 92 (FIG. 1) arrives at the objectdetection module 32 (FIG. 2).

At S1, object detection module 32 (FIG. 2) detects objects in a frame ofvideo input and identifies the object types thereof. The detection maybe tested by using an object classifier to compare the image of theobject with previously stored and continuously self-learning objectsstored in an objects library (see paper N. Dalal and B. Triggs,“Histograms of Oriented Gradients for Human Detection,” Proceedings ofthe IEEE Conference on Computer Vision and Pattern Recognition, SanDiego, USA, June 2005. Vol. II, pp. 886-893). Once an object isidentified from the image, the image area covering the object iscropped. Existing technology supports producing lower resolutionversions of an image. From the cropped area, at least one lowerresolution image of the original cropped area is produced and saved forfurther analysis along with the original cropped image. In later steps,the lowest resolution image of the cropped area is processed first andimages are processed in the order of lower resolution to higherresolution. Higher resolution images are processed for the purpose ofobtaining resolution context scores. Particularly, the resolutioncontext score module 37 (FIG. 2) analyzes increasingly higher resolutionimages of various regions and sub-regions of the image corresponding tovarious parts and sub-parts of the object. The analysis of a higherresolution image in turn includes calculating appearance scores forsemantic attributes, computing geometric scores and computing resolutioncontext scores for sub-regions which are of higher granularity than theregions in the lowest resolution image. The resolution for the lowestresolution image may be predetermined such as being stored as a constantin semantic attribute detection program 30 or provided as input via I/Odevice 28 (FIG. 2).

D2 maintains a list of semantic attributes and associated images. Inaddition to describing a semantic attribute, each semantic attributecorresponds to a body part. For example, semantic attributes“sunglasses,” “eyeglasses,” and “no glasses” all correspond to the bodypart “middle face region;” semantic attributes “beard,” “moustache,” and“no facial hair” all correspond to the body part “lower face region.”FIG. 5 shows examples of semantic attributes being associated with bodyparts according to an embodiment of the invention. The list of semanticattributes 52 (FIG. 1) contains both the semantic attributes and theircorresponding body parts.

At S2, the appearance score module 34 (FIG. 2) analyzes an image savedfrom S1, in real-time, or a delayed mode, by evaluating the probabilityof semantic attributes 52 (D2) being present at regions of the image. Asstated above, the lowest resolution image is analyzed first. Semanticattributes likely to be visible on the lowest resolution image may beevaluated at this stage while other semantic attributes likely to bevisible on a higher resolution image may be evaluated at a later step.The images of the semantic attributes are stored in a semanticattributes library which is continuously self-learning.

At S2, in evaluating the probability of semantic attributes beingpresent at regions of the image, aspects of the invention employ amethod described in the works of Viola et al. in “Robust Real-timeObject Detection,” Cambridge Research Laboratory Technical Report,February 2001. The method is further described with real-valuedconfidence scores in the works of Bo Wu et al. in “Fast RotationInvariant Multi-View Face Detection Based on Real Adaboost,” IEEEInternational Conference on Automatic Face and Gesture Recognition,2004. The method provides steps to calculate an appearance score torepresent the probability of an attribute being present at a region. Thepresence of a semantic attribute is evaluated through the application ofa semantic attribute detector. A detector for a semantic attribute is afunction that maps a region of an image into a real number in theinterval [0,1], where the output indicates the probability that thesemantic attribute is present in the image region given as input. Underthe invention, the resulted value of an appearance score can range from0 to 1. At each region of the image, there may be multiple appearancescores corresponding to the probability of multiple semantic attributesbeing present at the same region.

FIGS. 5A and 5B show examples of applying semantic attributes to a humanbody image according to an embodiment of the invention. In FIG. 5A,unlike prior art which would identify only image regions 60, 62, and 64as head, torso and legs respectively, embodiments of the inventionadditionally extract skin color from region 60, shirt color from region62, and pants color from region 64, etc. Similarly in FIG. 5B, region 66is not only identified as the upper face region, it may also provideattributes describing hair, baldness, or the presence of a hat. Region68 is not only identified as the middle face region, it may also provideattributes describing eyes, vision glasses or sunglasses. Region 70 isnot only identified as the lower face region, it may also provideattributes for mouth, moustache, or beard. In addition, the image ofFIG. 5A is of lower resolution than FIG. 5B. Attribute detectorsapplicable to the whole body, such as skin color, shirt color and pantscolor, are applied to lower resolution image in FIG. 5A, while attributedetectors specific to a face, such as hair style, presence of glassesand moustache, are applied to FIG. 5B.

Subsequently in S2 (FIG. 4), the appearance score module 34 (FIG. 2)applies a threshold value to all appearance scores resulted fromapplying semantic attribute detectors on the image. Appearance scoresless than the threshold value will be discarded while the remainingappearance scores will be kept. The threshold value may be predeterminedsuch as being stored as a constant in semantic attribute detectionprogram 30 or provided as input via I/O device 28 (FIG. 2). Afterapplying the threshold value, there still may be more than oneappearance score remaining at a region of the image. Each appearancescore at each region of the image corresponds to a semantic attribute.As described above, each semantic attribute corresponds to a body part.Hence, each appearance score at a region of the image also, correspondsto a body part. Then, each region having appearance scores above thethreshold value will be tagged with the corresponding body parts. As aresult, the output of the appearance score module 34 includes positionsof regions marked with appearance scores and tagged with semanticattributes and body part names, e.g., for region x, the appearance scoreis 0.6 and the tag is “beard/lower face region” with “beard” being thesemantic attribute and “lower face region” being the body part.

FIG. 5C shows examples of evaluating appearance scores according to anembodiment of the invention. Region 602 obtains three appearance scores,beard (0.1), moustache (0.1), and “no hair” (0.95). For example, thethreshold value is 0.5. As a result, as described above, “no hair” isselected as the attribute for region 602 because “no hair” receives ascore that is above the threshold value of 0.5. Similarly, region 604obtains three appearance scores, beard (0.9), moustache (0.2), “no hair”(0.1). Therefore, beard is selected as the attribute for region 604because beard receives a score that is above the threshold value of 0.5.As described above, both region 604 and region 602 will be tagged with abody part of “lower face region”. Region 604 may be later rejected forhaving a low geometric score as well as a low resolution context scoreaccording to the evaluation by the configuration optimization module inS5 (FIG. 4).

The output of S2 (FIG. 4) includes positions of regions marked withattributes and appearance scores and tagged with body part names. FIG.5D shows inputs and outputs for the step calculating appearance scoresaccording to an embodiment of the invention. In calculating appearancescores, the appearance score module 34 (FIG. 2) takes inputs 610, whichincludes a cropped image of an object 612, a list of semantic attributeswith corresponding parts 52, an image library of semantic attributes 620as references, and an appearance score threshold value 630. The outputs690 includes regions on the image with semantic attributes, part namesand appearance scores 650. The output appearance scores are all abovethe appearance score threshold value 630.

At S3 (FIG. 4), to compute resolution context scores for the imageprocessed in S2 (e.g., image x), the resolution context score module 37(FIG. 2) needs to analyze higher resolution images of image x. Asdescribed supra, the higher resolution images are produced and savedfrom S1. The main idea is that, if a body part is visible in an image ata given resolution, it should also be visible on the same image in ahigher resolution. For example, at a particular region, region y,semantic attribute “beard” is given a score of 0.9 and consequentlyregion y is tagged as “beard/lower face region”. In a higher resolutionimage, region y is expected to show sub-parts of the lower face region(e.g. mouth, chin, etc.). If it does not happen, it is likely that thebody part “lower face region” is actually not present in region y, and alow resolution context score would be assigned to region y.

FIG. 6 shows examples of evaluating resolution context scores accordingto an embodiment of the invention. Under a lower resolution image, onimage 700, the appearance score module 34 (FIG. 2) detects a face bodypart at region 702 by applying semantic attribute detectors such asbeard or eyeglasses or facial skin color. Image 750 is a higherresolution image of region 702. Since the availability of resolutioncontext score for a region depends on the availability of a higherresolution image for the region, with the availability of image 750, aresolution context score for region 702 on image 700 can be obtained.Under image 750, region 702 is evaluated to detect whether the face asdetected on image 700 contains expected sub-parts such as eyes, nose,and mouth. Relevant semantic attribute detectors such as beard oreyeglasses or even eye color may be applied to image 750. Accordingly,appearance scores are calculated on image 750 for the semanticattributes applied at regions such as region 704. In addition, geometricscores are calculated for the regions identified with semanticattributes that are above a predetermined threshold value. In short, thesteps S2 to S7 in FIG. 4 will be applied to image 750 to produce a totalscore and/or a weighted average score that is part of output 54 forimage 750. Each image produces output 54 when analyzed. The weightedaverage score from image 750 becomes the resolution context score forregion 702 on image 700.

FIG. 6A further illustrates how the resolution context score module 37arrives at a resolution score. In processing from a lower resolutionimage to a higher resolution image, image 670 at resolution N is a lowerresolution image than image 690 at resolution N+1. At region 675 onimage 670, the attribute of “a European face” has an appearance score of0.9. Image 690 examines region 675 at a higher resolution. The analysisprocess applied to image 690 includes calculating appearance scores byapplying semantic attributes, computing resolution context scores,computing geometric scores (described at a later step), performingconfiguration optimization (described at a later step), and computingtotal score (described at a later step). As described supra, the output54 includes a weighted average of the image's appearance scores,resolution context scores and geometric scores as described herein.Therefore, the weighted average score, 0.7 in this case, from output 54for image 690 is the resolution context score of region 675 on image670.

To further illustrate how region 675 on image 670 on FIG. 6A has aresolution context score of 0.7, assume that there are three regionsdetected on image 690 based on semantic attribute detectors beingapplied on image 690. Assume that the three regions are region x, regiony, and region z. Assume that the appearance scores for region x, regiony, and region z on image 690 are 0.9, 0.8, and 0.9 respectively. Assumethat geometric scores for region x, region y, and region z on image 690are 0.5, 0.6 and 0.35 respectively. Assume that there is a higherresolution image for region x, region y, and region z. Assume that thehigher resolution image of region x has two sub-regions, region xx andregion xy. Assume that region xx and region xy have no correspondinghigher resolution images. Assume region xx has an appearance score of0.95 and region xy has an appearance score of 0.9. Assume that thegeometric scores for region xx and region xy are 0.9 and 0.8respectively. Since there are no corresponding higher resolution imagesfor region xx and region xy, the resolution context score for region xxand region xy is 0. Assume that the weight factor for appearance score,geometric score and resolution context score is 0.5, 0.3 and 0.2 in allanalysis in the example. Therefore, the numbers can be represented inTable 1 for the highest resolution image corresponding to region x onimage 690.

TABLE 1 Region xx Region xy Weight Appearance score 0.95 0.9 0.5Geometric score 0.9 0.8 0.3 Resolution context score 0 0 0.2

The weighted average score for the highest resolution imagecorresponding to region x on image 690 is:

(0.95*0.5+0.9*0.3+0*0.2+0.9*0.5+0.8*0.3+0*0.2)/2=0.7275

The sum is divided by 2 because there are two regions (region xx andregion xy) in the calculation. The output of 0.7275 becomes theresolution context score of region x on image 690. Similarly, assumethat, upon analysis of the higher resolution images of region y andregion z, the resolution context scores for region y and region z are0.6 and 0.5 respectively. Table 2 depicts scores for region x, region yand region z on image 690 is shown below.

TABLE 2 Region x Region y Region z Weight Appearance score 0.9 0.8 0.90.5 Geometric score 0.5 0.6 0.35 0.3 Resolution context score 0.7275 0.60.5 0.2

Therefore, the weighted average score for image 690 is:

(0.9*0.5+0.5*0.3+0.7275*0.2+0.8*0.5+0.6*0.3+0.6*0.2+0.9*0.5+0.35*0.3+0.5*0.2)/3≈0.7

Because image 690 is the corresponding higher resolution image of region675 on image 670, region 675 on image 670 has a resolution context scoreof 0.7.

As further demonstrated in FIG. 6A, the existence of a resolutioncontext score for a region depends on whether a higher resolution imagefor that region is available for analysis. Therefore, the highestresolution image does not have resolution context scores. As a result,the weighted average score for output 54 for the highest resolutionimage will include the weighted average of appearance scores andgeometric scores only. Also, as demonstrated by FIG. 6A, image 690provides a resolution context score for region 675 on image 670. Otherregions on image 670 will have to go through similar analysis asdescribed above to arrive at their corresponding resolution contextscores.

The output of S3 (FIG. 4) included regions on the lowest resolutionimage with semantic attributes, part names and resolution contextscores. FIG. 6B shows inputs and outputs for the step evaluatingresolution context scores according to an embodiment of the invention.In calculating resolution scores, the resolution score module 37 (FIG.2) takes inputs 830 which include images of different resolutions 860and regions on lowest resolution image with semantic attributes, partnames and appearance scores 650. The outputs 880 include regions on thelowest resolution image with semantic attributes, part names andresolution context scores 885. In arriving at the final outputs, theresolution score module 37 may produce intermediate outputs includingregions on images of different resolutions with semantic attributes,part names and resolution context scores.

At S4 (FIG. 4), the geometric score module 36 (FIG. 2) computesgeometric scores by measuring the distances and angles among aparticular configuration of candidate regions under analysis andattempts to match the distances and angles among the candidate regionsto the geometric configuration of a human body. For example, the morelikely a configuration of candidate regions matches the naturaldisplacement of the human body, the higher a geometric score is givenfor each part in the configuration. In one embodiment, the algorithm tocalculate the geometric score is as follows: among the semanticattributes identified at step S2 (FIG. 4), extract part names from theattributes; for each part, the geometric score module 36 computes thedistances and angles from all other parts, or just a parent part, whendynamic programming is used for optimization, and use a standardclassification method (e.g., Naive Bayes Classifier athttp://en.wikipedia.org/wiki/Naive_Bayes_classifier) to give a scoreranging from 0 to 1 of how the distances and angles feature vectorcorresponds to a feasible configuration of the human body. Inembodiments, examples of computing geometric scores are provided asfollows.

Geometric Score (G_(i)) Examples

The geometric score (G_(i)) for body part i (or region i) may beexpressed in terms of a geometric score (G_(Ai)) based on angles and/ora geometric score (G_(Di)) based on distances.

In one embodiment, G_(i)=(G_(Ai)+G_(Di))/2, which is a straightarithmetic average.

In one embodiment, G_(i)=W_(A)G_(Ai)+W_(D)G_(Di), which is a weightedarithmetic average, wherein the weights (W_(A),W_(D)) are non-negativereal numbers satisfying W+W_(D)=1, and wherein the weights (W_(A),W_(D))are inputs that may be selected or determined, in one example, based onsuch factors as the relative accuracy and/or importance of referencevalues of angles and distance (see below) used to calculate thegeometric scores G_(Ai) and G_(Di).

In one embodiment, G_(i)=(G_(Ai)*G_(Di))^(1/2), which is a geometricaverage.

In one embodiment, G_(i)=G_(Ai), wherein only angles, and not distances,are used.

In one embodiment, G_(i)=G_(Di), wherein only distances, and not angles,are used.

Geometric Score (G_(Ai)) Based on Angles

Let Ai={A_(i1), A_(i2), . . . , A_(iN)} denote an array of N anglesdetermined as described supra for between part i (or region i) and eachpair of the other body parts (or regions).

Let a_(i)={a_(i1), a_(i1), . . . , a_(iN)} denote an array of Ncorresponding reference angles stored in a library or file, wherein N≧2.

Let δ_(Ai) denote a measure of a differential between A_(i) and a_(i).

In one embodiment, δ_(Ai)=[{(A_(i1)−a_(i1))²+(A_(i2)−a_(i2))²+ . . .+(A_(iN)−a_(iN))²}/N]^(1/2).

In one embodiment, δ_(Ai)=(|A_(i1)−a_(i1)|30 |A_(i2)−a_(i2)|+ . . .+|A_(iN)−a_(iN)|)/N.

Let t_(A) denote a specified or inputted angle threshold such that:

G_(Ai)=0 if δ_(Ai)≧t_(A); and

G _(Ai)=1−δ_(Ai) /t _(A) if δ_(Ai) <t _(A).

Thus, G_(Ai) satisfies 0≦G_(Ai)≦1. In particular, G_(Ai)=1 if S_(Ai)=0(i.e., if all determined angles are equal to all of the correspondingreference angles). Furthermore, G_(Ai)=0 if δ_(Ai)≧t_(A). (i.e., if themeasure of the differential between A_(i) and a_(i) is intolerablylarge).

Geometric Score (G_(Di)) Based on Distances

Let D_(i)={D_(i1), D_(i2), . . . , D_(iM)} denote an array of Mdistances determined as described supra between body part i (or regioni) and each other body part (or region).

Let d_(i)={d_(i1), d_(i2), . . . , d_(iM)} denote an array of Mcorresponding reference distances stored in a library or file, whereinM≧2.

Let δ_(Di) denote a measure of a differential between D_(i) and d_(i).

In one embodiment, δ_(Di)=[{(D_(i1)−d_(i1))²+(D_(i2)−d_(i2))²+ . . .+(D_(iN)−d_(iM))²}/M]^(1/2).

In one embodiment, δ_(Di)=(|D_(i1)−d_(i1)|+|D_(i2)−d_(i2)|+ . . .+|D_(in)−d_(iM)|)/M.

Let t_(D) denote a specified or inputted distance threshold such that:

G_(Di)=0 if δ_(Di)≧t_(D); and

G _(Di)=1−δ_(Di) /t _(D) if δ_(Di) <t _(D).

Thus, G_(Di) satisfies 0≦G_(Di)≦1. In particular, G_(Di)=1 if δ_(Di)=0(i.e., if all determined distances are equal to all of the correspondingreference distances). Furthermore, G_(Di)=0 if δ_(Di)≧t_(A) (i.e., ifthe measure of the differential between D_(i) and d_(i) is intolerablylarge).

FIGS. 7A and 7B show examples for evaluating geometric scores for anoptimal configuration according to an embodiment of the invention. InFIG. 7A, there are many parts identified on illustration 800, with eachsquare representing a region on the image that identifies a semanticattribute with part name. With many isolated parts identified, there aremany possible configurations possible to form the human body. The actualhuman body in the image is superimposed in FIG. 7A. For example, a headmay be detected at region 801. Two arms are detected at regions 803 and805 and two legs are detected at regions 807 and 809. FIG. 7Billustrates a set of regions on illustration 802 being selected as partof an optimal configuration by the configuration optimization module 38.The functionality of the configuration optimization module 38 isdescribed in the subsequent step. As shown in FIG. 7B, regions 801, 803,805, 807, and 809 are selected as parts of the optimized configuration.The geometric scores are calculated for each region in a givenconfiguration by measuring the angles and distances to other regions.For example, the geometric score of region 801 may be calculated frommeasuring the angles and distances of region 801 to all other regionsbelonging to a particular configuration candidate.

The outputs of S4 (FIG. 4) include a configuration of candidate partswhere each part (i) is associated with a semantic attribute, anappearance score A_(i), resolution context score R_(i), and geometricscore G_(i). FIG. 7C shows inputs and outputs for the step evaluatinggeometric scores according to an embodiment of the invention. Incalculating geometric scores, the geometric score module 36 (FIG. 2)takes inputs 810, which may include a candidate configuration of parts(set of parts with appearance scores and resolution scores) beinganalyzed by the optimization module 815, and a reference library ofangles and distances among parts 820. The outputs 890 include 850candidate configurations of parts where each part (i) is associated witha semantic attribute, appearance score A_(i), resolution context scoreR_(i), and geometric score G_(i).

At S5 (FIG. 4), the configuration optimization module 38 (FIG. 2) usesdynamic programming to select an optimal configuration based on theappearance scores, geometric scores, and resolution context scores.Given the set of candidates, there may be several possibleconfigurations that could be chosen as the final body parts region plusattributes estimation from the image. The optimal configuration, whichis the configuration having the maximal appearance, geometric, andresolution scores, is selected via dynamic programming, using thealgorithm proposed in “Pictorial Structures for Object Recognition,”Felzenszwalb et al., International Journal of Computer Vision (IJCV),January 2005. When an optimal configuration is selected, the selectedregions for the optimal configuration are already associated withsemantic attributes and have body part tags at the regions as describedabove.

Therefore, at S5 (FIG. 4), many possible candidate body configurationscan be derived from the available regions and their associated body parttags and attributes. The goal of S5 is to select the best configurationout of the many possible body configurations. The optimization modulesearches this space of configurations, aiming to determine theconfiguration with the highest weighted average score in terms ofappearance scores, resolution context scores, and geometric scores. Asan example, the configuration optimization module 38 may use the formulaas described supra used in conjunction with Tables 1 & 2 to compute aweighted average score for each possible configuration and select theone with the highest weighted average score as the output.

As an alternative to having predetermined weights for the three types ofscores when calculating the weighted average score, the weights can bedynamically determined. To compute an optimized weighted average scorefrom all three types of scores, S6 (FIG. 4) may determine the optimalweights for the scores. In determining the optimal weights, thestructured learning module 35 (FIG. 2) at S6 (FIG. 4) uses a machinelearning procedure called “structured learning”, described in “LargeMargin Methods for Structured and Interdependent Output Variables,”Tsochantaridis et al., Journal of Machine Learning Research (JMLR),September 2005. The basic idea includes presenting many examples of bodypart configurations, including their attributes, to the system. Thestructured learning module will then optimize the weights such that anyconfiguration in the presented example set has a higher overall scorethan invalid configurations that do not correspond to valid human bodyarrangements. Structured learning is also described by Tran et al. in“Configuration Estimates Improve Pedestrian Finding,” NationalInformation Processing Systems Foundation 2007. It is a method that usesa series of correct examples to estimate appropriate weightings offeatures relative to one another to produce a score that is effective atestimating configurations.

At S7 (FIG. 4) the compute total score module 39 (FIG. 2) computes anoptimized total score based on the appearance scores, geometric scores,and resolution context scores from the regions in the optimizedconfiguration. With the input from the structured learning module 35(FIG. 2), the compute total score module 39 utilizes the optimal weightsgiven to the appearance scores, geometric scores and resolution contextscores to calculate the optimized total score, which in turn producesthe weighted average score of the appearance scores, geometric scoresand resolution context scores by dividing the total score with thenumber of regions being analyzed.

Therefore, each configuration under analysis is composed of a set ofparts where each part (i) is associated with an attribute andcorrespondent appearance score A_(i), resolution context score andgeometric score G_(i). At S7 (FIG. 4) the compute total score module 39(FIG. 2) uses the following formula to compute the optimized totalscore:

${\sum\limits_{i}\; {W_{1}\left( A_{i} \right)}} + {W_{2}\left( G_{i} \right)} + {W_{3}\left( R_{i} \right)}$

where A_(i) represents appearance scores, G_(i) represents geometricscores, R_(i) represents resolution scores for each part i of theconfiguration, and W₁, W₂, and W₃ correspond to the weights obtained bythe structured learning module. W₁, W₂, and W₃ are provided by S6 thestructured learning module 35 (FIG. 2) through the method describedabove.

FIG. 8 shows inputs and outputs for the step of computing a total scoreaccording to an embodiment of the invention. Inputs 840 for the computetotal score module 39 (FIG. 2) include 842 candidate configuration ofparts where each part (i) has appearance score A_(i), resolution scoreR_(i), and geometric score G_(i), and 844 weights provided thestructured learning module. Once the total score is calculated, theweighted average score can be calculated by dividing the total scorewith the number of regions on the image being analyzed. The outputs 849include a score 847 which is the weighted average of A_(i), R_(i), andG_(i).

As used herein, it is understood that “program code” means any set ofstatements or instructions, in any language, code or notation, thatcause a computing device having an information processing capability toperform a particular function either directly or after any combinationof the following: (a) conversion to another language, code or notation;(b) reproduction in a different material form; and/or (c) decompression.To this extent, program code can be embodied as any combination of oneor more types of computer programs, such as an application/softwareprogram, component software/a library of functions, an operating system,a basic I/O system/driver for a particular computing, storage and/or I/Odevice, and the like.

The foregoing description of various aspects of the invention has beenpresented for purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formdisclosed, and obviously, many modifications and variations arepossible. Such modifications and variations that may be apparent to anindividual in the art are included within the scope of the invention asdefined by the accompanying claims.

What is claimed is:
 1. A method comprising: producing a plurality ofversions of an image of an object derived from a video input, whereineach version has a different resolution of said image of said object;computing an appearance score at each of a plurality of regions on thelowest resolution version of said plurality of versions of said imagefor at least one semantic attribute for said object, wherein saidappearance score denotes a probability of the at least one semanticattribute appearing in the region; analyzing one or more other versionsof the multiple versions to compute a resolution context score for eachof the plurality of regions in the lowest resolution version, whereinsaid resolution context score denotes an extent to which finer spatialstructure exists in the one or more others versions than in the lowestresolution version for each of the plurality of regions; and determininga configuration of the at least one semantic attribute in the lowestresolution version based on the appearance score and the resolutioncontext score in each of the plurality of regions in the lowestresolution version.
 2. The method of claim 1, comprising: displayingand/or storing said configuration.
 3. The method of claim 1, comprising:computing a geometric score for each region of said plurality of regionson the lowest resolution version, said geometric score computing aprobability of a region matching stored reference data for a referenceobject corresponding to the detected object with respect to angles anddistances among the plurality of regions.
 4. The method of claim 3,wherein the resolution context score for the lower resolution version ofsaid image is computed as a weighted average score computed from aplurality of scores for a next higher resolution version of said higherresolution versions of said image.
 5. The method of claim 4, whereinsaid plurality of scores for said next higher resolution version of saidimage comprise appearance scores and geometric scores.
 6. The method ofclaim 4, wherein said plurality of scores for said next higherresolution version of said image comprise appearance scores, geometricscores and resolution context scores.
 7. The method of claim 6, whereinsaid weighted average score for the next higher resolution version ofthe image is computed using the following formula divided by I:${\sum\limits_{i}\; {W_{1}\left( A_{i} \right)}} + {W_{2}\left( G_{i} \right)} + {W_{3}\left( R_{i} \right)}$wherein I represents the number of regions in the next higher resolutionversion of the image, i is a region index, Σ_(i) denotes a summationfrom i=1 to i=I, A_(i) represents appearance scores in region i, G_(i)represents geometric scores in region i, R_(i) represents resolutioncontext scores in region i, and W₁, W₂ and W₃ represent weightsrespectively assigned to the appearance scores, the geometric scores,and the resolution context scores.
 8. The method claim of 7, comprising:storing and/or displaying output of at least one portion of said imagein at least one version of said higher level versions of said image withspatial information on semantic attributes.
 9. A computer programproduct comprising: a computer readable storage device having computerreadable program code embodied in the storage medium, said computerreadable program code containing instructions that perform a method forestimating parts and attributes of an object in video, said methodcomprising: producing a plurality of versions of an image of an objectderived from a video input, wherein each version has a differentresolution of said image of said object; computing an appearance scoreat each of a plurality of regions on the lowest resolution version ofsaid plurality of versions of said image for at least one semanticattribute for said object, wherein said appearance score denotes aprobability of the at least one semantic attribute appearing in theregion; analyzing one or more other versions of the multiple versions tocompute a resolution context score for each of the plurality of regionsin the lowest resolution version, wherein said resolution context scoredenotes an extent to which finer spatial structure exists in the one ormore others versions than in the lowest resolution version for each ofthe plurality of regions; and determining a configuration of the atleast one semantic attribute in the lowest resolution version based onthe appearance score and the resolution context score in each of theplurality of regions in the lowest resolution version.
 10. The computerprogram product of claim 9, said method comprising: displaying and/orstoring said configuration.
 11. The computer program product of claim 9,said method comprising: computing a geometric score for each region ofsaid plurality of regions on the lowest resolution version, saidgeometric score computing a probability of a region matching storedreference data for a reference object corresponding to the detectedobject with respect to angles and distances among the plurality ofregions.
 12. The computer program product of claim 11, wherein theresolution context score for the lower resolution version of said imageis computed as a weighted average score computed from a plurality ofscores for a next higher resolution version of said higher resolutionversions of said image.
 13. The computer program product of claim 12,wherein said plurality of scores for said next higher resolution versionof said image comprise appearance scores and geometric scores.
 14. Thecomputer program product of claim 12, wherein said plurality of scoresfor said next higher resolution version of said image compriseappearance scores, geometric scores and resolution context scores. 15.The computer program product of claim 14, wherein said weighted averagescore for the next higher resolution version of the image is computedusing the following formula divided by I:${\sum\limits_{i}\; {W_{1}\left( A_{i} \right)}} + {W_{2}\left( G_{i} \right)} + {W_{3}\left( R_{i} \right)}$wherein I represents the number of regions in the next higher resolutionversion of the image, i is a region index, Σ_(i) denotes a summationfrom i=1 to i=I, A_(i) represents appearance scores in region i, G_(i)represents geometric scores in region i, R_(i) represents resolutioncontext scores in region i, and W₁, W₂ and W₃ represent weightsrespectively assigned to the appearance scores, the geometric scores,and the resolution context scores.
 16. The computer program product ofclaim 15, said method comprising: storing and/or displaying output of atleast one portion of said image in at least one version of said higherlevel versions of said image with spatial information on semanticattributes and associated parts.
 17. A computer system comprising aprocessor and a computer readable memory unit coupled to the processor,said computer readable memory unit containing instructions that when runby the processor implement a method for estimating parts and attributesof an object in video, said method comprising: producing a plurality ofversions of an image of an object derived from a video input, whereineach version has a different resolution of said image of said object;computing an appearance score at each of a plurality of regions on thelowest resolution version of said plurality of versions of said imagefor at least one semantic attribute for said object, wherein saidappearance score denotes a probability of the at least one semanticattribute appearing in the region; analyzing one or more other versionsof the multiple versions to compute a resolution context score for eachof the plurality of regions in the lowest resolution version, whereinsaid resolution context score denotes an extent to which finer spatialstructure exists in the one or more others versions than in the lowestresolution version for each of the plurality of regions; and determininga configuration of the at least one semantic attribute in the lowestresolution version based on the appearance score and the resolutioncontext score in each of the plurality of regions in the lowestresolution version.
 18. The system of claim 17, said method comprising:displaying and/or storing said configuration.